Alkylation of hydrocarbons



`yam. i9, i943.

R. F. MARSCHNER ETAL ALKYLATION OF HYDROCARBONS Filed Jne 18, 1941 55 YST m 0 w f5 C0 fp WM im m M u .M 0

Patented Jr 19, 1943 ALKYLATIoN or aoc .e

Robert F. Marsehner, Homewood, nl., and non R. v

Carmody, Hammond, Ind., rs to Standgigil Company, Chicago, nl., a corporation of Application June 18, 1941, Serial. N0. 398,556

Claims. (Cl. 1U16-J9) I'his invention relates to the production of normally liquid hydrocarbons from normally gaseous hydrocarbons and relates more particularly to the alkylation of isoparainic hydrocarbons with olenic hydrocarbons in the presence of a catalyst.

For many years. it has been customary to subject petroleum hydrocarbons to cracking operations for the production of gasoline. One of the by-products from this operation is a varying amount of normally gaseous hydrocarbons, usually comprising a mixture of olenicand paraiilnic hydrocarbons in various proportions. These by-product hydrocarbons were considered in the nature of waste gases until recent years when it has been realized that they are a valuable source of initial stock'for the production of definite hydrocarbons suitable either as aviationl gasoline or as motor fuels of high octane number. Various commercial operations have been pro- Y posed and employed for the conversion of the gaseous hydrocarbons to normally liquid hydrocarbons of gasoline boiling range, including such processes as polymerization plus hydrogenation. alkylation, etc. The products from these processes have proved so valuable that various hydrocarbons from other sources are now being diverted for conversion purposes, including gases from natural gas and from the light ends of products from distillate well. Cracking, dehydrogenation and isomerization have been employed for the conversion of paralnic hydrocarbons to feed stocks suitable for these processes. Alkylation is perhaps a more desirable method of obtaining hydrocarbons suitable for gasoline than, for example polymerization, since there is no need for subjecting the alkylation product to hydrogenation in order to obtain saturated hydrocarbons of high octane number. Branched-chain hydrocarbons other than isobutane (the only normally gaseous isoparafllnic hydrocarbon) are also occasionally diverted to allwlation in order toobtain additional amounts oi.' higher boiling hydrocarbons of high octane number.

It isan object of this invention to provide an improved process for the alkylation` of isoparamnic hydrocarbons, and more speclcally thel alkylatlon of isobutane with normally gaseous olens to' produce saturated branched-chain 'hydrocarbons within the gasoline boiling range.

Another object of our invention is to provide an improved alkylation processemploying a specific type of catalyst under certain conditions oi operation. A further object of our invention is to provide a process i'or the-optimum conversion branched-chain hydrocarbons suitable for 4use as aviation fuels. An additional object is to provide' a process wherein isobutane is alkylated with a minimum of degradationto undesirable byproducts. It is alsdan object of our invention to provide a process .for the production primarily of monoalkylate from the reaction of an isoparaiiiin and an olefin Other objects and advantages of our invention will become apparent as 4 the description thereof proceeds. v In the drawing: f

aluminum chloride in the catalyst'. on the rate of alkylation; and

Figure 2 is a plot depicting graphically the effect of the ratio of olen reacted to isoparain present on the production of monoalkylate.

Brieily stated, our invention contemplates the alkylation of an isoparaln such asisobutane with an olen such as ethylene in the'presence of a particular catalyst comprising an aluminum halide-hydrocarbon complex under` 'restricted conditions of temperature, pressure,ratio of reactants, and amount of activator. Aluminum chloride has been employed for -the alkylation of isoparalns by oleilns, aswell as' numerous other hydrocarbon conversion -processes, and it has been found by experiment that, generally speaking, pure aluminum chloride-is too act've" to be entirely satisfactory as a catalyst; i. e., the activity of the aluminum chloride as such is so great that numerous unwanted side reactions occur, such as polymerization, cracking,` isomerization, etc. Various methods have been proposed for modifying the catalytic activity of this compound. For example, very low temperatures can be employed such that cracking and polymerization are substantially avoided and the reaction is primarilyone of alkylation.` Such temperatures, however, require much longer periods for the reaction to become complete and therefore are neither advisable nor desirable com--l mercially. It has also been found that when reacting aluminum chloride withI a normally lliquid hydrocarbon, a complex or "red oil is formed which is still catalytically active but in which the activity is considerably modiiied. 'I'he particular type of hydrocarbon with which the aluminum chloride reacts determines,- to a marked degree, the type of complex which is formed, and complexes formed irom'the various types of hydrocarbons, such as oleilns, straightchain paraillns, branched-chain paraiins, naphthenes or aromatics, -diier considerably in their eectiveness in promoting an oleiin-paramn alkylation reaction. Moreover, it has been proposed to form denite 'complexes between an aluminum halide and a hydrocarbon byemployl ing such methods of synthesis -as' theGrign'ard reactionv wherein the halogen of the aluminum halide is replaced by one or'more hydrocarbon radicals. We have found that an valuminum Figure 1 is a plot depicting graphically eiect of the ratio of bound" hydrocarbon to halide-hydrocarbon complex prepared by the direct reaction of an aluminum halide with a saturated hydrocarbon is superior to the complexes formed by the reaction of the metal halide with other classes of hydrocarbons, and of the saturated hydrocarbons, the isoparafllnlc hydrocar- A bons yield a complex of especially desirable activity.

The active liquid aluminum halide-hydrocarbon complex employed in our alkylation reaction is prepared by the action of an aluminum halide, such as anhydrous aluminum chloride or aluminum bromide, and an activator comprising a hydrogen halide or a. compound affording a hydrogen halide, on a substantially saturated fraction containing predominantly at least one paraffln hydrocarbon preferably having at least two side chains. The reaction is carried out at a temperature in the range of from about 50 F. to about 175 F. 'I'his liquid catalyst complex is suitably prepared from aluminum chloride and a substantially saturated fraction containing paramn hydrocarbons having at least six total carbon atoms, with at least two side chains per molecule. Such saturated fractions include, for example, the hydrogenated polymers and copolymers of olefins having less than six carbon atoms per molecule, namely, ethylene, propylene and the butylenes and amylenes, and the products of alkylation of isobutane and of isopentane with such olens are particularly suitable. These fractions are very rich in highly branched parafnnic hydrocarbons, for example, isohexanes,'iso heptanesor isooctanes. We prefer to prepare our complex from a fraction rich in isooctanes, although fractions more volatile or less volatile but rich in branched-chain hydrocarbons are also effective in producing the desired complex, and fractions containing linear parailinic hydrocar- A bons are included.

As an example, an aluminum chloride-hydrocarbon complex was prepared by stirringtogether at atmospheric pressure a quantity of anhydrous aluminum chloride with an excess of commercial isooctane and a minor amount of hydrogen chloride at liiill F. to 140 F. until a liquid complex resulted. D uring the complex formation large'amounts of isobutane were produced and the remaining hydrocarbon liquid contained a quantity of material of a higher boiling range than that present in the original isooctane. The viscosity of the complex catalyst thus produced was below 1,000 seconds Saybolt viscosity at 100? F. and the complex was easily pumpable. The complex contained approximately 35% by weight of hydrocarbons. No complete and adequate analysis of the hydrocarbons joined to the alumiconverted to complicatedring structures with' g5 varying degrees of saturation and unsaturation.

'I'heir analysis, of course, is unimportant except in so far as it serves to distinguish the complex from those formed, for example, by means of the Grignard reaction employing alkyl h alides and magnesium.

Throughout the speciilcation and claims whenev'er the term "aluminum chloride-parailinic hydrocarbon complex" or paraillnic complex is employed, it is intended to designate the liquid 5 containing bound" hydrocarbons.

complex formed by the reaction of an aluminum halide with a parafiinic hydrocarbon in accordance with a procedure of the general type described above. We also refer to our complex as This is to designate that the hydrocarbon is Joined to the aluminum halide by chemical means, and to distinguish it from such catalysts as those comprising a slurry or solution of an aluminum halide in a liquid hydrocarbon.

In carrying out our alkylation process, isobutane and ethylene for example, are contacted with the catalyst so that there is an intimate mingling of the feed stocks and the catalyst. This can be accomplished by adding the isobutane to the complex with vigorous stirring and introducing the ethylene into the mixture, or the isobutane and ethylene can be intimately contacted and the mixture injected into contact with the complex. Various mechanical expedients can be employed for assuring intimate contact between the reactants and catalyst, such as for example, mechanical stirrers, tubular reactors, packed towers, turbo mixers, jet injectors, etc.

desirable commercially. In continuous operation, the catalyst and reactants can flow concurrently or cormtercurrently Moreover, instead of a single tower, with means for intimate contact, we can use a series of towers, and introduce the olenic hydrocarbons into each tower in small increments. The catalyst and reactants, as well as the product, can 'flow from tower to tower concurrently or countercurrently, or we can employ separate catalyst beds in each tower and direct only the'hydrocarbons through the entire system. l

The catalyst, although it can be used in the form in which it is obtained from the reaction of the isoparafiinic hydrocarbons and aluminum halide, is advantageously cut bac with anhydrous aluminum chloride so` that the composition of thecontentsis from about 23% to about of bound" hydrocarbons. This can be done by adding powdered anhydrous aluminum chloride to the complex previously prepared, to yield a Vsubstance of denite over-all aluminum chlorideto-bound hydrocarbon ratio, and this complex of limited aluminum chloride-to-bound hydrocarbon ratio constitutes our preferred catalyst.

Figure 1 illustrates the effect of employing an aluminum chlorlde-isoparamnic hydrocarbon complex having various amounts of bound hydrocarbon in the complex as a catalyst in the alkylation of isobutane with ethylene, employing otherwise substantially identical conditions cf temperature, pressure, amount of activator and ratio of reactants. The weight percent of .bound" hydrocarbons in the catalyst is plotted along the absclssa, and the rate of alkylation along the ordinate. The rate of alkylation is expressed in terms of gallons of alkylate produced per pound of aluminum chloride per hour. It is obvious from the graph that the rate is much greater when the weight percent of bound hydrocarbon in the catalyst lies between about 23% and about 32% than it is for lower or higher percentages of hydrocarbon, peak activity being tain such a catalyst near peak activity, itis only The process can be carried out batchwise orl continuously, the latter method being the most 32%, and most desirably about 28% by weight4 2,sos,ss1

pound of complex per hour, and preferably'aty a.

rate of from about 5 to about 20 cubic feet per pound of complex per hour to obtain the optiv mum conversion. At rates very much higher than this, and particularly at rates above about 50 cubic feet of .olefin per pound of catalyst per hour, not only is there grave danger of the reactants passing through unchanged, but temperature control becomes much more diiilcult. A't rates below that set forth, the contact between olefin and paraiiin in the large volume of catalyst becomes more difficult, and polymerization may occur to an undesirable extent. The type of apparatus employed will influence to some extent the rate of olen addition. If a wide, shallow tower or a tubular reactor of large diameter is employed, then obviously some additional means for mixing must be employed in order -to obtain adequate contact between the reactants and the catalyst.

'I'he alkylation is preferably carried out in the presence of an activator, employing for that purpose minor amounts of a hydrogen halide, such as hydrogen chloride or hydrogen bromide, or a substance affording a hydrogen halide under the reaction conditions such as an alkyl halide. Hydrogen chloride and ethyl chloride are particularly desirable activators. The amount ot hydrogen halide should be 4% or less by weight, based upon the aluminum chlorideior aluminum bromide in the complex, and may be as low as 0.5%.

We have found that thepresence oi hydrogen duringvthe reaction slows the rate of alkaylation and therefore hydrogen should preferably be excluded from the reaction. f

In order to 'obtain optimum yields oi' monoalkylate per unit of time it is necessary to use a rather critically controlled ratio of reactants. When using up to about 0.6 mol of ethylene reacted per mol of isobutane present, .the product is fairly uniform. When using greater amounts o1' ethylene, 'the amount of lower octane number,

not affected during the conversion and should be discarded from the system at the completion of the reaction. Figure 2 illustrates graphically the eii'ect of the mol ratio of ethylene to isobutane on the production oi' monoalkylate-i. e.,

hexane. The mol ratio of ethylene to isobutane l has been plotted along the abscissa and the percent by volume yield of monoalkylate along the ordinate. The conditions employed for the various points were substantiallyidentical for each run except for the ratio of ethylene to isobutane, and fall well within the preferred range. It will be at once apparent that the yield of monoalhlate falls' of! appreciably when the mol ratio of ethylene to isobutane is above -about 0.6. The yield of dialkylate and higher boiling hydrocarbons increases, however, as will be shown` later.

Although' alkylation will occur at temperatures within the range 0f from -about 0 to about 212 F., or higher, desirable to carry out thealkylation at temperatures within the range of from about to about F. and most desirably at about 125 11'. At lower temperatures the rate of alkylation is slower and the amount of heavy alkylate is increased, while at higher temperatures the production of cracked" or redistributed products which are much less desirable is greatly in- The pressure should be superatmos'pheric and, while it can` include a range oi' from about'30 pounds per square inch up to about 500 pounds per square inch, we prefer that it be maintained below 150 pounds per'square inch, although the exact pressure employed does not aect the alof the other variables do. In all cases thev Dressure is sufficiently great to maintain the reactantsin the liquid or dissolved phase under the conditions of temperature employed, and usually an ethylene partial pressure of about pounds Per Square inch is employed. l

The following table will illustrate the advantages of carrying out an alkvlation process under the conditions herein set forth. Various runs show deviations from the preferred conditions. and the consequent loss oi' efliciency either as regards yield, product distribution or reaction rate. In all cases the runs were made using isov butane and ethylene as the reactants, and eml ploying an aluminum chloride-isoparamnic hyhigher boiling paraillns, especiallyjthose above l the usual gasoline range, gradually increases. We therefore desire to convert from about 20% to about 40%l Der pass of the isobutane or other isoparains in order to secure the best over-all result. The ethylene stream to the alkylation v reaction can-be an ethylene-ethane stream containing as little as-7% ethylene. The ethane is so.

drocarbon complexcontaining at least 23% by weight o f "bound hydrocarbon. Samples of come ot the Products were analytically fractionated on a laboratory column having an emciency six, seven and eight atoms per molecule, anda residual cut containing hydrocarbons having nine or more carbon4 atoms per molecule were taken.

vWe have found that `lt is highly l Included octanes.

Runs A, B and C are illustrative of operation under our preferred conditions, runs A and B differing chiey in the rate, while run C was carried out at much lower temperature than the, other two runs. Runs D and E were carried out at a temperature below our preferred range, and illustrate admirably the effect of such deviation from the preferred conditions, since the amount of dialkylate formed is undesirably increased the yield is smaller and the reaction rate is low. In run F the temperature was above the range desired, and although it will be noted that the yield of alkylate based on ethylene was greatly increased, the product distribution shows that considerable cracking, etc., took place, the volume of pentanes being greatly increased at the ex pense of the more desired monoalkylate hexanes.

Run G illustrates the eilect of too great an amount of activator, the yield of monoalkylate being reduced with the formation of large quantities of pentanes. In run H, the mol ratio of ethylene to isobutane has been increased to 1.15; consequently the yield of dialkylate (octanes) and higher boiling hydrocarbons has greatly increased, with a consequent decrease in monoalkylate. In the nal column oi' the table the preferred conditions are summarized. When more than one of the operating conditions falls outside oi.' these preferred ranges, deviation from the optimum becomes more pronounced and the yield of monoalkylate is correspondingly reduced, or the rate of conversion becomes uneconomically low.

Although we have described our process relative to the alkylationof isobutane with ethylene. it should be understood that this is by way of illustration and not by way of limitation, and that the use of other olenic hydrocarbons, such as propylene, the butylenes, etc., is contemplated, as well as the use of other low-boiling isoparafilnic hydrocarbons such as isopentane or even isohexane.

We claim:

1. A process for alkylating isoparafiinic hydrocarbons with olenic hydrocarbons which comprises contacting said lsoparailinic hydrocarbons with said oleiinic hydrocarbons in the presence oi a catalyst containing an aluminum halide-paramnic hydrocarbon complex having from about 23% to about 32% by weight of bound hydrocarbons, and a hydrogen halide activator under conditions of temperature, pressure and ratio of reactants adapted to promote the reaction of said isoparailnic hydrocarbons with said oleflnic hydrocarbons.

2.l A process for alkylating isoparafnc hydro carbons with oleiinic hydrocarbons which comprises contacting said isoparaillnic hydrocarbons with said olenic hydrocarbons in the presence ot an aluminum halide-parafiinic hydrocarbon complex containing from about 23% to about 32% by weight, of bound hydrocarbons 'and in the presence of a small amount ot a hydrogen halide activator under conditions of temperature, pressure and ratio oi reactants adapted to promote the reaction of said isoparalnic hydrocarbons with said olenic hydrocarbons.

3. A process for alkylating isoparaillnic hydrocarbons with olenic hydrocarbons which comprises contacting said isoparafhnic hydrocarbons with said olenic hydrocarbons in the presence of an aluminum halide-parailnic hydrocarbon complex containing about 28% by weight of bound hydrocarbons and in the presence oi a small amount ot a hydrogen halide activator under conditions of temperature, pressure and ratio of reactants adapted to promote the reaction of said isopara'ilinic hydrocarbons with said olenic hydrocarbons.

4. A process according to claim 2 in which said oleilnic hydrocarbons are added at a rate oi from 5 to 20 cubic feet per pound of said complex per hour.

5. A process according to claim 2 ln which said aluminum halide-paraffinic hydrocarbon complex is an aluminum chloride-parainic hydrocarbon complex.

6. A process for alkylating isoparaiiinic by: drocarbons with olenic hydrocarbons which comprises contacting said isoparafilnic hydrocarbons with said olenlc hydrocarbons in the presence of a catalyst containing an aluminum halide-parafilnic hydrocarbon complex having from about 23% to about 32% by weight oi bound hydrocarbons and a hydrogen halide activator at a temperature within the range of from about 80 F. to about 150 F. under conditions o! pressure and ratio of reactants adapted to promote the reaction ot said isoparamnic hydrocarbons with said oleilnic hydrocarbons.

'1. A process for alkylating isoparailinic hydrocarbons with oleilnic hydrocarbons which comprises contacting said isoparafilnic hydrocarbons with said olenic hydrocarbons in the presence of a catalyst containing an aluminum halideparamnlc hydrocarbon complex having from about 23% to about 32%l by weight of bound hydrocarbons and in the presence of an eiective amount but not more than 4% of a hydrogen halide activator under conditions of temperature, pressure and ratio of reactants adapted to promote the reaction of said isoparafilnic hydrocarbons with said olenlc hydrocarbons.

8. A process for alkylating isoparainic hydrocarbons with olenic hydrocarbons which comprises contacting said isoparafllnic hydrocarbons with said olenic hydrocarbons in the presence of a catalyst containing an aluminum halideparailnic vhydrocarbon complex having from l about 23% to about 32% by weight of bound hydrocarbons and a hydrogen halide activator, the mol ratio of said oleilnlc hydrocarbons to said isoparailinic hydrocarbons being less than 0.6, under conditions of temperature and pressure adapted to promote the reaction of said isoparamnic hydrocarbons with said oleiinic hydrocarbons.

9. A process for alkylating isoparainic hydrocarbons and olenic hydrocarbons which comprises contacting said isoparamnic hydrocarbons with said oleiinic hydrocarbons in the presence of an aluminum halide-paraflinic hydrocarbon complex containing from about' 23% to about 32% by weight of bound hydrocarbons and in the presence of an enective amount but not more than 4% by weight, based on the aluminum chloride present, oi' a hydrogen halide activator at a. temperature of from about to about F. in theliquid phase, the mol ratio of said oleiinic hydrocarbons to said isoparamnic hydrocarbons being less than 0.6.

10. A process according to claim 9 in which said isoparaiiinic hydrocarbons contain less than six carbon atoms per molecule.

11. A process according to claim 9 in which said oleilnic hydrocarbons contain not less than tmc nor more than five carbon atoms per molec e.

12. A process for alkylating isobutane with ethylene wiwi". Wr"rises contacting said isoparamnic hydrocarbons with oleflnic hydrocarbons which comprises maintaining in a contacting zone an alwlation catalyst consisting essentially of an aluminum halide-paralnic hydrocarbon complex, maintaining in said complex from about 23% to about 32% by weight of bound hydrocarbons, continuously introducing isoparafllnic hydrocarbonsand olenic hydrocarbons along with a small amount of a hydrogen halide activator into said zone and continuously withdrawing alkylation products therefrom. maintaining the temperature of said contacting zone within the approximate range of about 80 to 150 F., employing a pressure in said contacting zone suilcient for maintaining the reaction mixture in liquid phase at the reaction temperature and maintaining in said contacting zone 20 mation of hexaneswithout a moi ratio of olefinic hydrocarbons to isoparafilnic hydrocarbons for effecting the formation oi' mono-alkylate without producing substantial amounts of diallqlate.

14. The procs of alkylating isobutane with ethylene which comprises contacting isobutane and ethylene in a contacting zone with a catalyst consisting essentially of an aluminum halide-paranic hydrocarbon complex contain- 10 ing from about 23% to about 32% by weight of bound hydrocarbons in thepresence of a small amount ,of hydrogen halide at a temperature within the approximate range of 80 to 150 F. under sulcient pressure to maintain the reac- 15 tion mixture substantially in liquid phase, using an amount of catalyst in the reaction zone corresponding to at least 10% based on isobutane in said zone, and maintaining an ethylene to isobutane ratio in said zone for effecting the forproducing substantial amounts of octanes. l

15. 'I'he process ot claim 14 wherein the temperature is in the general vicinity of 125 F. and the mol ratio is in the general vicinity of 0.5 mols 25 of ethylene per mol of isobutane.

` ROBERT F. MARSCHNER.

DON R. CARMODY. 

